1. Field of the Invention
The present invention relates to modular multiple disk drive assemblies.
2. Background Art
Greater quantities of data are being generated and stored by computer systems. Some data, such as intermediate calculations, is discarded almost immediately. However, an increasing amount of data must be stored for extended periods of time. This period of time may range from minutes to years depending on the type of data, type of application which generates or uses the data, and requirements imposed by government regulations, business practices, historical needs, and the like.
Long term data storage must often meet apparently conflicting performance criteria. Ideally, all storage should have a low cost-per-bit of data stored. This stored data must be stored and readily retrievable in a brief period of time. This time may be measured in a variety of ways, such as the time before the first data is transferred, the amount of data received each second, the total access time for a given quantity of data, and the like. Space required to store the data becomes an increasingly important parameter as the amount of data increases. Additionally, high reliability is required for stored data. This reliability can be achieved through the use of highly dependable storage devices, through the use of systems for correcting or recovering data, through redundancy of storage equipment, and the like.
Traditionally, no one type of storage device has been able to satisfy cost, speed, density and reliability requirements. High performance magnetic disks have been used as a first level of data storage due to their high data rates and low access times. However, high performance magnetic disk systems tended to be relatively expensive and low density. Secondary storage for backup, archiving and very large storage requirements has typically been provided by magnetic tape. Magnetic tape offered greater storage density and lower cost-per-bit than high performance magnetic disk systems, but often suffered from greatly increased data access time.
Increasingly, a wide gap is developing between the characteristics of high performance disk systems and tape systems. Various attempts at providing an intermediate level of long term storage have not met with great commercial success. One technique is to use a collection of inexpensive, low performance disks. An example of low performance disks are those meeting the ATA standard such as those used in many personal computers. However, implementing groups or arrays of these inexpensive, low performance disks exhibit certain difficulties. For example, inexpensive disks are typically incompatible with high speed media interfaces such as Fibre Channel (FC), SCSI, iSCSI, ESCON and the like. Another problem with arrays of inexpensive disks is that such arrays tend not to provide any increase in storage density over high performance disk systems. Yet another problem with arrays of inexpensive disks is that such arrays are typically designed for special purpose use only and are not compatible or configurable for use with a large number of high performance computer interfaces or applications.
The present invention fulfills the need for intermediate storage with performance characteristics similar to high performance disk systems as well as cost and density characteristics comparable to tape systems. Storage assemblies include programmable logic allowing each assembly to appear as a wide variety of different storage devices. The present invention includes data storage assemblies having multiple data storage units, such as disk drives or other data storage devices, co-located onto a replaceable assembly. In one embodiment, multiple storage assemblies are integrally connected to a single chassis for ease of hot plug insertion and removal.
The present invention provides for scalable and incremental increase of storage capacity and performance. The modular design provides for sharing of power and cooling facilities, thus reducing product cost and simplifying manufacturing and reliability. The ability to work with any high performance data storage interface allows data storage units to be utilized to maximum potential. Data storage units, such as ATA disk drives, are connected within small groups so that aggregate performance and functional capabilities can be combined into a higher performing complete storage assembly.
In one embodiment of the present invention, each module contains five ATA disk drive assemblies. Individual data storage assemblies contain control electronics and a data connection interface which presents and emulates the electrical image of a single disk drive, tape drive, tape library or the like for connection to industry standard FC interfaces. These modules may be held in a single chassis. An implementation with ten modules contains a total of fifty individual disk drives, providing a high performance architecture that aggregates benefits of the individual disk drives in a very condensed package. This architecture also provides a compact means of providing a high capacity, high band width data storage solution at minimal production cost. This architecture also integrally contains sufficient modularity to provide scalable storage capacity with new assemblies. New generation disk storage capacity or other technologies may easily be incorporated into the modular assemblies to provide increased flexibility in product implementation.